Retrieve image bytes from image file path

I've been unable to find a post that details how to retrieve the image bytes from an image (given the file path of the image on the device). Basically, using the FilePicker, I'm able to get the path of an image that the user chooses:

file:///store/samples/pictures/Bridge.png

Now, I'm looking to get the bytes for this image, so that I can send it to a server. Can anyone provide me with some sample code, or perhaps refer me to another post?